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Biomedical subjects

B M O'Brien

Publications and source records attributed to B M O'Brien.

At least 55 records · Page 3Linked to original sources
PubMed1989

Glutaraldehyde-tanned microvascular grafts.

In this study the efficacy of preserving microvascular heterografts with glutaraldehyde tanning was investigated. These were compared with glutaraldehyde-tanned autografts. Previous studies have found that untreated autograft veins maintain a 95% patency rate, whilst untreated heterograft veins (Group 1) had a 15% patency rate at 4 weeks in this study. Autogenous glutaraldehyde-tanned rabbit carotid arterial grafts (Group 2) and glutaraldehyde-tanned human chorionic veins (Group 3) were interposed in rabbit femoral or carotid arteries. Fifty per cent and 75% patency rates were achieved respectively at 4 weeks. The low patency rate of the autogenous group suggests that the glutaraldehyde tanning technique itself is largely responsible for the low patency of glutaraldehyde-tanned human chorionic veins rather than any immunological response. Therefore if human chorionic veins are to be used as a readily available preserved microvascular graft, further investigation is required to develop another technique which will reduce antigenicity without promoting thrombosis.

Animals↗
PubMed1989

Liposuction in the treatment of lymphoedema; a preliminary report.

Liposuction was used in the treatment of primary and secondary lymphoedema in 19 patients. Seven patients had no previous surgical treatment and 12 had previously been treated with microlymphaticovenous anastomoses and/or surgical reduction. There was subjective improvement in 11 of the 13 patients available for follow-up. There was objective improvement in 10 of the 11 patients with unilateral lymphoedema, with an average reduction of 23% of the excess volume. Seven of the 13 patients were on conservative treatment prior to liposuction. The average reduction in this group was 20.5%. The average follow-up time was 9.5 months. From this preliminary report it can be concluded that liposuction, either as a primary procedure or as an adjunct, can be a useful procedure in the treatment of both primary and secondary lymphoedema.

Arm↗
PubMed1989

An assessment of different types of anastomosis with significant vessel disproportion using thin-walled interposition vein grafts.

The microvascular anastomosis of vessels with a diameter difference in the range of 3:1 can be a difficult surgical exercise, with the risk of bleeding or thrombosis. Five different techniques for dealing with such asymmetries were investigated in a series of autogenous rabbit vein grafts. An assessment was made of patency rates and of factors involved in the performance of the anastomoses. It is concluded that the end-to-end with oblique cut procedure is the most suitable for the clinical situation.

Anastomosis, Surgical↗
PubMed1989

Lower limb reconstruction in children using expanded free flaps.

Controlled expansion is a technique that increases the area of local tissue available for reconstruction. An extension of this is to expand free flaps prior to elevation, thereby increasing their area. This has been particularly useful in children where there may be insufficient tissue available at free flap donor sites. Four children have had extensive cutaneous defects of the lower limb reconstructed with expanded parascapular free flaps. Measurements indicate an approximate doubling in skin area. There has been normal growth of the affected limbs and there has been no donor site morbidity. Apart from small areas of narrow marginal necrosis at the tip of the flaps in the first three cases, which were of no consequence, healing at the recipient site was complete.

Child↗
PubMed1989

Factors involved in salvaging ischaemic rabbit skin flaps: ATP and free radicals but not thromboxane.

Rabbit epigastric free flaps were subjected to ischaemia at 25 degrees C for 24 hours. At the time of revascularisation the flaps were infused intra-arterially with one of the following: Hanks balanced salt solution (control), the high energy phosphates PEP/ATP, the thromboxane synthetase inhibitor dazoxiben hydrochloride, the free radical scavenger SOD and a combination of all these agents (treated groups). Control ischaemic flap survival at post-ischaemia day 7 was 23.5%, while the other treatments resulted in improved flap survival of 43.5% (p less than 0.025), 23.5% (not significant), 38.6% (p less than 0.05) and 35.7% (p less than 0.05) respectively. None of these agents improved post-ischaemic blood flow significantly. These results would support the use of PEP/ATP or SOD in the clinical treatment of failing ischaemic skin flaps but do not support the use of dazoxiben hydrochloride.

Adenosine Triphosphate↗
PubMed1989

Comparative study of vascularized and nonvascularized tendon grafts for reconstruction of flexor tendons in zone 2: an experimental study in primates.

Vascularized tendon grafts were compared with nonvascularized tendon grafts in a primate experimental model. In four monkeys, seven vascularized extensor hallucis longus grafts were placed in the foot's digital fibroosseous canal and these were compared with eight nonvascularized tendon grafts similarly placed in the opposite extremities. The juncture techniques and postoperative protocols were identical for both tendon groups. All tendons were explored 5 months after insertion. The vascular pedicle was patent in all vascularized tendons. Three tendon ruptures occurred in nonvascularized tendons and only one rupture occurred in a vascularized tendon. The digits with vascularized tendons demonstrated a significantly better simulated total active motion (117 degrees versus 128 degrees, p less than 0.05) than digits with nonvascularized tendons. The difference was even more significant when a localized tenolysis of the proximal juncture of the tendon graft was performed (215 degrees versus 138 degrees, p less than 0.01). This study supports the concept that vascularized tendon grafts may be advantageous in scarred tendon beds.

Animals↗
PubMed1989

Comparative study of the use of prefabricated bone tendon grafts and conventional tendon grafts in flexor tendon reconstruction.

In tendon grafting the weakest area is the junction between the grafted tendon and bone. In dogs a strong union between tendon and bone can be produced by threading the flexor carpi radialis tendon through a hole drilled in the radius. In experimental repair of canine flexor tendons, 3 weeks after operation the strength of the union between a composite bone-tendon graft prepared in this way is double that of the bone-tendon junction of a conventional graft. Use of prefabricated bone-tendon grafts should permit earlier postoperative movement and limit formation of adhesions between a tendon graft and its bed.

Animals↗
PubMed1989

Coumarin and 7-hydroxycoumarin treatment of canine obstructive lymphoedema.

1. Canine obstructive lymphoedema was created in one hind leg of 30 dogs by irradiation of the groin and surgical removal of surviving lymph glands and lymphatics. The opposite leg served as a control. Once the oedema had stabilized, groups of 10 dogs were treated orally with 12.5 mg day-1 kg-1 for 8 months with either one of the benzopyrones coumarin (2H-1-benzopyran-2-one) and 7-hydroxycoumarin (7-hydroxy-2H-1-benzopyran-2-one), or placebo. 2. The two benzopyrones significantly (P less than 0.01) but gradually reduced the oedema by 20-30% over 8 months, as judged by circumferential measurements of the oedematous and control limbs. There was no change with the placebo. 3. In the oedematous fluids (lymph and interstitial fluid), benzopyrone treatment reduced the protein content and increased acid and neutral proteinase activity compared with the control limbs, while the levels of the proteinase inhibitor alpha 2-macroglobulin remained unchanged. Furthermore, these active drugs reduced the excess water content, thickness and hydroxyproline content of skin biopsies from oedematous limbs compared with those from control limbs. No changes were observed for the placebo group. 4. These biochemical changes suggest that benzopyrones can reduce the excess proteinaceous fluid in lymphoedema by increasing the levels of proteinase activity relative to the number of proteinase inhibitors. As a secondary event the amount of fibrosis in the skin is also reduced, presumably by an increase in collagenase activity from the mononuclear phagocytes. 5. These results support the hypothesis that benzopyrones activate the production of proteinases by mononuclear phagocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Prior elevation of vascular island skin flaps: intolerance to ischemia caused by venous obstruction.

Previous experiments in our laboratory have shown that prior elevated flaps, those elevated 24 hr prior to complete ischemia, are more tolerant of the ischemic insult than acutely ischemic flaps that have had no prior elevation. In the current study, the effect of prior elevation was observed on tolerance to ischemia caused by venous occlusion alone. Under these conditions, limited blood flow may be possible via the unclamped artery, so a state of partial ischemia exists. After seven hours of venous obstruction, acutely elevated flaps had a 50 percent survival rate at postoperative day 7. This was significantly better (p less than 0.005, chi 2 test) than the 0 percent survival rate for prior elevated flaps for the same period of venous obstruction. It is speculated that the more rapid generation of cytotoxic free radicals during the period of partial ischemia is more detrimental to the prior elevated flaps that have greater blood flow, than to the controls.

Animals↗
PubMed1989

The deleterious effect of arteriovenous flow reversal during experimental free muscle transfer.

Arteriovenous flow reversal (AVR) has been used experimentally to salvage ischemic limbs and to create novel skin flaps with some success. The clinical applicability of AVR in muscle by way of two arteriovenous anastomoses in the rabbit was investigated. Twenty-four rabbits were divided into two groups. In Group 1 (control), the rectus femoris muscle was harvested and transplanted in the opposite thigh, anastomosing the donor femoral artery to the recipient femoral artery, and the donor rectus femoris vein to the recipient femoral vein. In Group 2 (flow reversal), the same procedure was done except the donor artery was anastomosed to the recipient vein and vice versa. Six and 24 hr postoperatively, specimens were compared macroscopically and by weight and histology. Reversed flow muscles were significantly heavier than control muscles at 6 hr and at 24 hr. Histologically, 6 hr of AVR caused edema, intramuscular hemorrhage, neutrophil infiltration, and thrombosis of most vessels. By 24 hr muscle cell degeneration was well advanced. All control muscles were viable, with only mild edema and slight peripheral necrosis. Possible reasons for the failure of AVR in muscle are discussed. On the basis of these results, AVR in free muscle transfer is not advocated.

Animals↗
PubMed1989

The effect of time of vascular island skin flap elevation on tolerance to warm ischemia.

The effect of time of vascular island skin flap elevation on tolerance to a subsequent 12-hour period of warm ischemia was studied. Sixty rats were separated into five equal groups; the rat epigastric island flap was used as the model. In group 1 flaps were elevated and immediately subjected to 12 hours of complete ischemia by application of microvascular clamps to both artery and vein of the pedicle. In group 2 the flap was elevated, and after 12 hours of recovery ischemia was induced for 12 hours. Groups 3 to 5 were similar to group 2 except that the time interval between initial elevation and subsequent ischemia varied: 24 hours for group 3; 72 hours for group 4; 144 hours for group 5. Necrosis was evaluated on postoperative day 7. Those flaps elevated 24 hours before ischemic insult (group 3) had significantly better survival than all other groups (p less than 0.025 at least). There were no significant differences between the other groups. Flap elevation 24 hours before a complete ischemic episode significantly increased tolerance to ischemia. Elevating a flap earlier or later than 24 hours did not have any significant benefit.

Animals↗
PubMed1989

The effect of prior elevation of skin flaps and ischemia on blood thromboxane levels.

The physiological factors that allow for the survival of ischemic skin flaps have not been clearly elucidated. Previous work by others has shown that elevation of a flap 24 hours before an episode of complete ischemia significantly improved survival, presumably by delaying the onset of the no-reflow phenomenon. The current study, using an epigastric flap, investigated the role of thromboxane in these events by observing postischemic plasma levels of thromboxane B2, the stable metabolite of the short-lived thromboxane A2. Acutely ischemic flaps were compared with those elevated 24 hours before ischemia. After the ischemic insult, blood was drawn from the venous effluent of the flaps. Thromboxane levels after 4 hours of ischemia were significantly decreased (p less than 0.001) in the postischemic period in those flaps elevated 24 hours before ischemia compared with flaps that had undergone ischemia acutely. Moreover, acutely ischemic flaps had significantly more thromboxane than nonischemic controls (p less than 0.001). These results confirm the importance of thromboxane metabolism in the no-reflow phenomenon.

Animals↗
PubMed1989

Hydrostatic distention and pharmacological treatment of epinephrine-induced microarterial spasm.

The efficacy of using hydrodistention and vasodilatory drugs to relieve spasm in arteries was investigated. The femoral arteries of 64 rabbits (divided into five groups) were placed in spasm by the topical application of epinephrine (1 mg/ml). In group A (controls) vasospasm was induced without further treatment. In group B vasospasm was induced, and the arteries were hydrodistended with normal saline. In three additional groups vasospasm was induced and either 10% lidocaine hydrochloride (group C), verapamil hydrochloride (group D), or chlorpromazine hydrochloride (group E) was applied. Thirty minutes later the vessels were hydrodistended. All vessels were measured at set intervals, and some specimens were retained for light and electron microscopy. All methods of spasm relief were successful, although to varying degrees. Hydrodistention alone produced the widest dilation for the longest time. Lidocaine was the most successful drug treatment alone. Verapamil followed by hydrodistention was the most successful combination regimen, but did not produce better results than hydrodistention alone. Hydrodistention alone produced significant arterial wall damage, resulting in permanent structural modifications. Prior vasodilatory drug treatment reduced but did not eliminate hydrodistention damage. Although hydrodistention dilates for longer periods than vasodilatory drugs, the arterial wall damage associated with hydrodistention indicates that it should be used only when all other methods of vasodilation have failed.

Animals↗
PubMed1989

The beneficial effect of chlorpromazine on dorsal skin flap survival.

A 3 x 10-cm dorsal rat skin flap contains a distal portion that is poorly perfused. The dorsal flap served as a useful model to test hemodynamic properties of the vasodilatory drug chlorpromazine. A control group of flaps were treated with saline and the test group with chlorpromazine (15 mg/kg intraperitoneally). Eight days postoperatively, the surface area of the flaps that necrosed was 27.3% for the treated group and 36.5% for the controls. Using Student's t-test this difference was significant (p less than 0.001). Nutrient blood flow determined by the penetration of fluorescein dye into the flap was consistently greater in the chlorpromazine-treated group compared with the control group in the first 24 hours postoperatively. The adenosine triphosphate (ATP) levels measured at 0 and 24 hours postoperatively were consistently lower in the distal parts of the flap, treated or control, compared with proximal parts of the flap (p less than 0.001, analysis of variance). However, there were no significant differences in ATP levels between treated and control biopsies at any one site on the flap. In conclusion, chlorpromazine had a beneficial effect on rat skin survival, and increased blood flow appears to be one of the major reasons.

Animals↗
PubMed1989

Creation of distal canine limb lymphedema.

A canine model of distal limb lymphedema was established in order to study the treatment of this condition by lymph node transfer. This model was more difficult to establish than whole-limb lymphedema. Significant edema was achieved by a combination of preoperative irradiation and circumferential removal of skin from the irradiated areas followed by removal of the contents of the popliteal fossa. Despite these measures, it was not possible to produce lymphedema in every case, possibly because of the presence of lymphaticovenous shunts and panvascular compensation mechanisms.

Animals↗